Today's Scleral Lens

Scleral lenses are now universal––used not only for irregular cornea patients, but also to treat high refractive errors and presbyopia.

By Gregory W. DeNaeyer, O.D.

Release Date: JUNE 2012

Expiration Date: JUNE 1, 2015

Goal Statement:

This article will present an update on today's scleral lenses and outline their ability to treat patients with irregular cornea, high refractive errors and presbyopia.

Faculty/Editorial Board:

Greg W. DeNaeyer, O.D.

Credit Statement:

This course is COPE-approved for 1 hour of CE credit. COPE ID is 34757-CL. Please check your state licensing board to see if this approval counts toward your CE requirement for relicensure.

Joint-Sponsorship Statement:

This continuing education course is joint-sponsored by the Pennsylvania College of Optometry.

Disclosure Statement:

The author has no financial relationships to disclose.

The recent resurgence of
scleral contact lenses has
significantly improved our
success in managing patients with
corneal irregularity and ocular
surface disease (OSD).1-4 Patient
and practitioner demand for scleral
contact lenses has pushed manufacturers to improve existing products and to develop new designs.
New materials and solutions also
have helped to improve the success
of scleral contact lenses.

This article will review the latest updates in materials, solutions,
designs and fitting techniques that
will continue to advance the success of scleral lenses.

Classification

The fitting characteristics and
functionality of gas-permeable
(GP) lenses are directly related
to their diameter. Therefore, it's
critical that a universal classification system be employed so that
practitioners can use designs that
have predictive characteristics.
The Scleral Lens Education Society (SLS) has recently designed a
classification system that defines
GP lenses on both size and fitting
characteristics (see "Terminology"):5,6

Corneal lenses (8mm to 12.5mm) are supported completely by the cornea. Corneal
contact lenses do not hold a
tear reservoir.

Corneal-scleral lenses (12.5mm
to 15mm) extend beyond the
limbus, and are supported by
both corneal and scleral tissue.
Corneal-scleral lenses hold a
limited tear reservoir.

Scleral lenses (15mm to
25mm) place all lens bearing
on the sclera. Scleral lenses are
further subdivided as: mini-scleral lenses (15mm to 18mm)
which have a somewhat limited tear reservoir capacity,
and full scleral lenses (18mm
to 25mm) which have an
almost unlimited tear reservoir
capacity.

This classification system allows
manufacturers to design and market scleral lenses for specific types
of patients. Practitioners can then
utilize these products with predictive results.

Materials

The advent of hyper-Dk materials
has significantly reduced hypoxic-related complications associated
with scleral lens use. Using materials with Dk values of 100 or more
is important with scleral lenses,
because they semi-seal to the eye,
making tear exchange relatively
slow as compared to corneal GP
designs. To prevent lens flexure,
scleral lenses often are manufactured with thicknesses four times
greater than that of corneal GPs.
Using hyper-Dk lenses to maximize
oxygen helps to compensate for
permeability decreases secondary to
increased lens thickness.

Occasionally scleral lenses will
exhibit poor on-eye wettability
(figure 1). If this occurs soon after
the lens is dispensed, then it is
most likely due to lab-related over-polishing or residual lab debris.
Patients who have OSD may also
have difficulty wetting a scleral
lens secondary to their tear quality.
In either case, the wettability can
almost always be restored by plasma treating the lens. Instruct the lab
to plasma treat each lens ordered and have lenses treated as needed if
wettability decreases during the life
of the lens.

Solutions

As with any other type of contact lens, solutions play an important role in the success of scleral
contact lens wear. Scleral lenses
can be cared for using approved
GP lens cleaning and disinfecting
products or off-label use of multipurpose soft lens solutions. Using
preserved solutions with scleral
lenses puts the patient at a greater
risk for toxic reactions because
residual solution can become
trapped underneath the lens,
which increases exposure time
to the anterior ocular surface.
Prescribing a hydrogen peroxide-based care system eliminates
exposure to any potential toxins
or antigens.

Scleral contact lenses have to be
filled with saline before application
to prevent trapped air bubbles that
compromise both fit and vision.
Unfortunately bottled saline solutions contain preservatives that
could induce a toxic reaction.

Bottled, non-preserved solutions are available but pose two
potential risks. First, there is the
possibility of contamination if the
bottle is used over several days.
Secondly, although non-preserved,
most of these solutions still contain
a buffering agent that can be toxic
to the patient.7,8

Alternatively you can prescribe
off-label use of 0.9% sodium
chloride solution that comes in
3ml single-use vials (figure 2). The
sodium chloride vials do not contain any buffers and eliminate the
risk of contamination because they
are single use.

Designs

There has been a dramatic
increase in available scleral lens
designs in the last five years (see
"Scleral Lens Designs"). All
of these designs require a diagnostic
set for successful lens fitting. Fitting
sets generally have diagnostic lenses
that have increasing amounts of sag-ittal depth with standard peripheral
curves or haptic section.

Determining which lens design to
use can be a challenging first step to
scleral lens fitting. Visiting with the
various manufacturers that are represented as exhibitors at contact lens
meetings can be a great way to learn
which designs will be most beneficial
for your practice.

One of the major differences
between available scleral lenses is
the amount of customization that
can be done on a specific design.
Some scleral lenses offer only a limited amount of change that can
be made to the standard parameters represented by the diagnostic
lens. For the novice scleral lens fitter, this can be somewhat helpful
because it can simplify the fitting
process. However, some patients
may require more creative changes
to achieve a successful fit; for these
cases, using a lens design that has
unlimited customization will be
beneficial.

Toric and quadrant-specific
design. Most standard manufactured
scleral lens designs have spherical
front and back surface optic zones.
Normally, this design setup fits the
patient adequately because the lenses
are vaulted completely off the cornea
surface; therefore, corneal toricity or
irregularity is often not a factor.

Scleral lenses effectively mask
both regular and irregular astigmatism by means of liquid reservoir.
Residual astigmatic error from a
scleral lens correction is often the
result of lens flexure that can be
eliminated by increasing the center
thickness of the lens or improving
the lens fit. Occasionally, residual
astigmatism can manifest from the
crystalline lens and thus is not inherently corrected for by the scleral
lens. If the amount of residual astigmatism is significant, the patient can
wear glasses over their scleral lenses
to correct the astigmatic error. Alternatively, the scleral lens can be manufactured with front surface toricity.
In this case, the lens will need to be
ballasted to orient and stabilize the
lens position.

Typically, scleral lens designs
come with a standard spherical back
surface haptic. It is now known that
the scleral is not spherical, but non-rotationally symmetrical.2 Scleral
asymmetry worsens with increasing
distance from the corneal limbus.
Minor differences between the
spherical lens haptic and the sclera
may be offset due to the spongy
scleral conjunctiva.

Some patients have asymmetric
scleral anatomy that results in a poor
fitting relationship when fit with
a scleral lens that has a spherical
haptic surface. These poorly fitting
lenses often exhibit a with-the-rule
appearance. The lens will have 3
o'clock and 9 o'clock compressions,
as well as excessive lift at the 6
o'clock and 12 o'clock positions. In
these instances, some manufacturers offer toric back surface haptic
(peripheral curves), which can dramatically improve the scleral lenses
fitting relationship.

Some practitioners report routinely using back surface haptic designs
for their scleral lens fits. Esther-Simone Visser, M.Sc., and colleagues
reported significant increases in comfort, visual quality and overall satisfaction when patients were switched
from back surface spherical designs
to back surface toric designs.9 Anecdotally, patients with toric back surface haptics report less accumulation
of reservoir debris trapped between
the lens and the eye during wear.

A few labs are able to manufacture scleral lenses with quadrant-specific curves for either the back
surface optical zone or the haptic
portion when troubleshooting an
extremely complex scleral lens fit.
For these cases, optical coherence
tomography (OCT) of a diagnostic
lens is helpful in determining quadrant-specific changes.

Multifocals. Scleral lenses primary have been used to improve
distance vision for patients who have
corneal irregularity. Recently, however, there has been some interest in
using multifocal scleral lenses to correct presbyopia. Theoretically, multi-focal scleral lenses could be used for
patients who have either regular or
irregular corneas. Scleral lenses don't
translate on the eye, so the available
multifocal scleral lens designs incorporate simultaneous designs with
center near optics. Unfortunately,
multifocal optics may not work well
for the irregular corneal patient if
they have significant corneal scar
tissue or significant residual higher-order aberrations.

Notching Lenses

Scleral GP lenses fit onto the
sclera. Scleral GP lenses can fit over
mild pinqueculas, but their firm
nature prevents them from draping
scleral obstacles that have significant
elevation. In these cases, a notch can
be beveled into the scleral lens so
that the lens bypasses the obstacle.
Scleral notches can improve the fit
for patients who have moderate to
severe pinqueculas or conjunctival
blebs resulting from trabeculectomy.

A diagnostic lens that is notched
can be kept in the office for fitting
purposes. Photos of the diagnostic lens can be sent to the lab for
evaluation and modification of the
notch that will be beveled into the
prescribed scleral lens. Notches have
to be kept shallow because they will
induce bubbles if they are cut too
deep. For this reason, it's best to use
a corneal-scleral lens or mini-scleral
lens because a relatively smaller lens
will require a shallower notch.

When the lens is dispensed, we
instruct the patient to insert it like a
puzzle piece so that the notched area
is aligned with the scleral obstacle.
At the follow-up visit, monitor the
patient to make sure that the lens is
still adequately clearing the obstacle
and not creating any tissue disruption, which is especially important in
the case of conjunctival blebs.

Piggybacking Lenses

For the irregular cornea patient,
scleral lenses are considered the
lens of choice when all other design
modalities have failed. Most of
the time, as long as the diameter
is large enough, a scleral lens can
completely vault up over almost any
cornea. There are rare cases where
the practitioner will have a difficult
time with complete corneal clearance
resulting in some areas of lens touch.

If the patient is asymptomatic
and their cornea is without any
disruption, then lens changes aren't
always necessary and the patient
can be monitored. However, if the
patient is symptomatic--especially if
the cornea shows epithelial disruption that is associated with the lens
touch--then the practitioner needs
to address the fitting relationship
immediately.

It is best if the lens vault or design
can be changed to improve the fit. If,
however, the practitioner is unable
to improve the fitting relationship,
then a soft lens placed under the
scleral lens can be used as a piggyback system. The soft lens effectively
cushions the cornea against any
scleral lens-related bearing.

If a standard molded design fits
on the cornea reasonably well, then
start with a daily disposable silicone
hydrogel (SiHy) lens that the patient
wears underneath the best-fit scleral
contact. A daily disposable eliminates the need for multiple solutions
and prevents lens-related solution
interactions. A SiHy lens will help to
maximize oxygen to prevent hypoxic-related complications.

If a standard molded soft lens
design does not adequately fit, then
a custom fit lathe cut design can be
used. Diameters larger than 14.5mm
may interfere with the lens haptic to
sclera relationship and disrupt the
scleral lens fit.

Lens Application

Scleral lens application is challenging because of the relatively
increased overall lens diameter.
Patients who are disabled and/or
elderly may especially have trouble
effectively applying scleral lenses.
Dalsey Adaptives, LLC has developed the See-Green device that can
be used to help patients successfully
apply their scleral contact lenses.10 The See-Green system comes with
a stand that holds a lighted plunger
(figure 3). Using this system, the
patient no longer has to hold the
lens, but rather lowers their eye onto
it, which leaves both hands free for
improved lid control. The light at the
center of the plunger is used as a target to allow for central positioning.

Scleral lens use has increased
exponentially over the last five
years. Utilization of scleral lenses
has expanded beyond the irregular
cornea, as practitioners are now
using scleral lenses for patients with
high refractive errors and presbyopia. Solution, material and design
updates will continue to improve
scleral lens fitting success.